Simulation strategies for the LHC ATLAS experiment

The ATLAS experiment, operational at the new LHC collider, is fully simulated using the Geant4 tool. The simulation program has been built within the ATLAS common framework Athena. The simulation software for the ATLAS Experiment at the Large Hadron Collider is being used for large-scale production of events on the LHC Computing Grid. This simulation requires many components, from the generators that simulate particle collisions, through packages simulating the response of the various detectors and triggers. All of these components come together under the ATLAS simulation infrastructure. The latest developments went into the direction to better represent the reality of the detector in all the possible details. The latest developments provide increased functionality and robustness. The full process is constantly monitored and profiled. Increased performance guarantee the best use of available resources without any degradation in the quality and accuracy of the simulation itself. In the presentation emphasis is put on validation efforts, performance tests, CPU and memory optimizations through the description of the entire process.